Overview - Chorionic villus sampling

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Chorionic villus sampling (CVS) is a test you may be offered during pregnancy to check if your baby has a genetic or chromosomal condition, such as Down's syndrome, Edwards' syndrome or Patau's syndrome.

It involves removing and testing a small sample of cells from the placenta (the organ linking the mother's blood supply with her unborn baby's).

When CVS is offered

CVS isn't routinely offered to all pregnant women. It's only offered if there's a high risk your baby could have a genetic or chromosomal condition.

Getting your results

The first results of the test should be available within 3 working days and this will tell you whether a major chromosomal condition, such as Down's syndrome, Edwards' syndrome or Patau's syndrome, has been discovered.

If rarer conditions are also being tested for, it can take 2 to 3 weeks or more for the results to come back.

If your test shows that your baby has a genetic or chromosomal condition, the implications will be fully discussed with you. There's no cure for most of the conditions found by CVS, so you'll need to consider your options carefully.

You may decide to continue with your pregnancy, while gathering information about the condition so you're fully prepared, or you may consider having a termination (abortion).

What are the alternatives?

An alternative to CVS is a test called amniocentesis. This is where a small sample of amniotic fluid (the fluid that surrounds the baby in the womb) is removed for testing.

It's usually carried out between the 15th and 18th week of pregnancy, although it can be performed later than this if necessary.

This test has a similar risk of causing a miscarriage, but your pregnancy will be at a more advanced stage before you can get the results, so you'll have less time to consider your options.

If you're offered tests to look for a genetic or chromosomal condition in your baby, a specialist involved in carrying out the test will be able to discuss the different options with you, and help you make a decision.